In the field of batteries, and in particular batteries designed for heavy duty and marine applications, it is typical to supply a battery with battery terminals in the form of a threaded bolt. This threaded bolt terminal allows a user of the battery to attach various electrical leads (which contain an end portion having an insulated ring connector) to the battery terminal by sliding the ring connectors over the threaded terminal and then securing the ring connectors by use of a threaded wing nut or other type of nut. In order to attach such a threaded bolt terminal to a battery, manufactures of batteries typically insert mold a bolt into a lead-alloy subassembly, which subassembly is then connected to the battery's cells using methods commonly known in the art.
The insert molding of the battery terminal bolt into the lead-alloy subassembly presents a myriad of manufacturing and structural issues. Because the threaded portions of the bolt must be exposed for connection to electrical leads, the threaded portion of the bolt must be located outside of the mold cavity so as not to be encased with the lead-alloy. From a manufacturing standpoint, a problem with prior insert molding of battery terminal bolts is that poor shut-off characteristics (i.e., the seal between the mold itself and the bolt) allow for the lead-alloy to leak out of the mold cavity and onto the battery terminal bolt's threads. This leakage had the unintended and undesirable consequence of possibly preventing a firm connection between the battery leads and the battery terminal due to the wing nut, or other nut, being interfered with by the lead-alloy. Typically, where a shut-off point is designed around a bolt's threads, the lead will leak out of the mold cavity due to the helical profile of the bolt's threads. Also, if the shut-off point of the bolt is designed around the shank (i.e., the non-threaded portion of the bolt), this will also typically lead to leakage because of irregular surface and dimensional variations in the shank.
From a structural standpoint, the lead subassembly in which the battery terminal bolt is encased typically has relatively shallow dimensions since it must fit within the plastic cover of a battery. Accordingly, the head of the battery bolt (which is encased in the lead-alloy subassembly and is typically a hex-head bolt) must not be too deep along its longitudinal axis. Otherwise, a sufficient amount of lead-alloy will not be present above and below the battery bolt head, which can lead to a user inadvertently pulling out the bolt during normal use or the bolt working its way out of the subassembly through normal operation of the machinery to which it is attached, which presumably will generate a fair amount of vibration. Typically, a battery bolt's head and washer thickness must lie within a restricted profile envelope of less than 0.25 of an inch.
Also, from a structural standpoint, the battery terminal bolt must be able to withstand so-called “abusive field torque failures”, which result, for instance, where a user applies too much torque to the wing nut or other nut attached to the terminal when tightening the nut. Such increased torque often times results in the battery bolt head rotating within the lead subassembly, therefore stripping the lead-alloy attachment points from the battery bolt head and causing a poor electrical connection between the battery bolt terminal and the battery's cells and/or leads. Such abuse field torque failures cannot be repaired, and require a user to purchase a new battery.
Accordingly, there is a need for a battery terminal bolt that will have increased shut-off capabilities during an insertion mold process.
There is also a need for a battery terminal bolt that will have sufficient pull-out strength while resisting abusive field torque failures.
Other needs will become apparent upon a review of the following detailed description, taken in conjunction with the drawings.